The invention concerns a valve arrangement which may occupy at least two positions for the purpose of pressure control and which is associated with a control apparatus by which the operability of the valve arrangement may be controlled. The valve arrangement may particularly be utilized in an anti-locking control system, such as described in U.S. Pat. No. 4,005,910.
Systems are already known in which valve arrangements are used, the failure of which causes a breakdown of the overall system. This in turn greatly jeopardizes the safety of persons.
An acute danger of accident may thus arise when a valve arrangement in an anti-locking system fails to operate in the desired manner. This is, for example, the case with an anti-locking system possessing an intake and an outlet valve when the intake valve fails to release the brake line upon actuation or even more when the outlet valve fails to close resulting in no pressure on the brake. The malfunctioning of a check valve, for example one which either bridges the intake valve or is inserted into the return supply line, may disrupt the operation of the system and herewith conjure up the danger of an accident. The danger of a failure is further increased by the fact that these parts, those of an anti-locking system, are relatively rarely actuated, namely only with locking danger.
It has therefore been proposed to actuate the valves with each starting of the vehicle in a control process and additionally to examine, with the aid of a monitoring apparatus, whether actuation of the valve has really taken place. In the aforementioned case, the valve arrangement is a so-called modulator in which a flexible wall, which may be shifted through pressure admission, closes a valve located in the brake line when locking is imminent and enlarges the expansion chamber for the pressure medium which is housed between this valve and the wheel brake cylinders. The functionally appropriate movement of the flexible wall is monitored by means of a switch and a monitoring apparatus.
The underlying mission of the invention is to extend this fundamentally known potential of monitoring from valve arrangements to seating valves.
This mission is accomplished through the features set forth herein.
With seating valves, the distance which the valve closing body travels between the "valve closed" and "valve already penetrable" positions is very short even when the distance to the terminal position "valve open" is long by choice. It is therefore difficult, particularly with consideration of valve tolerances, to detect the position "valve totally closed" by measuring techniques. Th solve this problem the invention suggests a combination of a seating valve and a slide which on the one hand exhibits a slight leakage flux and on the other hand a comparatively large and therewith easily determinable (by measuring technique) distance between a closed position and "valve beginning to open".
The ideas according to the invention may be employed with magnetically actuatable valves but also with pressure controlled valves such as check valves. In order to control the functional performance of such a check valve one supplements it with a preferably electromagnetically actuatable operating device which one activates from time to time. The reaction of the valve is monitored by measuring technique.
With the aforementioned magnet valve just as with the electromagnetically actuatable operating device one may separate the magnetic part from the hydraulic or pneumatic parts respectively. The combination valve closing body/slide becomes actuated here over a tappet.